A switch IC in which a switching circuit is formed on an SOI (Silicon On Insulator) substrate is utilized as a high-frequency switch because of its small capacitance resulting from the substrate. Such a high-frequency switch IC can be formed in an existing silicon process without using an expensive compound semiconductor and a complicated process peculiar to processing the compound semiconductor, and thus it is suitable for cost reduction. Moreover, since the high-frequency switch IC can also include a CMOS (Complementary Metal Oxide Semiconductor) circuit in the same chip, high integration of the high-frequency switch IC and miniaturization of a high-frequency switch module incorporating the IC therein are possible.
Thereby, an SPnT (Single Pole n Throw) high-frequency switch circuit in which an antenna terminal is used as an input terminal and a plurality of connection terminals between the switch circuit and a transmission circuit and a reception circuit as output terminals and a control circuit can be formed into one chip on the SOI substrate. When a plurality of output terminals is present, since wiring lengths within the chip from the input terminal to respective output terminals are different, an input impedance of the high-frequency switch IC when viewed from the input terminal is different depending on which one of the output terminals the input terminal connects to. Hence, depending on combination of the input terminal and output terminals, the high-frequency switch IC will mismatch with characteristic impedance of the high-frequency line of the antenna, resulting in increase of reflection loss of the high-frequency switch IC. As a result, variation in output characteristics of the high-frequency switch IC will be large among the output terminals.